<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
  <style>
    .nav { /*0,0,1,0 是nav 的  不是li的*/
      color: red;
    }
    li { /*0,0,0,1 */
      color: skyblue;
    }
  </style>
</head>
<body>
<nav class="nav">
  <ul>
    <li>继承的权重为0</li>
  </ul>
</nav>
</body>
</html>
